Tannin extract and process of making same.



, siderable traces of alumina.

g UNITED STATES IPatented July 28, 1903.

PATENT OFFICE.

GEORG KLENK, OF HAMBURG, GERMANY.

TANN IN EXTRACT AND PROCESS OF MAKING. SAME.

SPECIFICATION formingpart of Letters latent No. 734,889, dated July 28, 1903. Application filed May 20. 1903. Serial No. 157,947. (No specimens.)

To an whom it may concern:

Be it known that I, GEORG KLENK, doctor of philosophy, a citizen of the German Empire,residing at 20 Billhornerkanalstrasse,

Hamburg, Germany, have invented certain Improvements inTanning Extracts and Processes of" Making the Same, of whichthe following is a specification.

According to the United States Patent No. 720,157 granted to me liquid tannin extracts, which being sufficiently decolorized are soluble in cold water, are obtained by treating the crude tannin solution first with alumina sulfate and subsequently with sodium bisulfite. As pointed out in my application for Letters Patent filed April 3, 1903, Serial No.

150,989, the same liquid extracts may be obf tained by heating thethus-treated tannin solutions in a closed receptacle to a temperature between 120 to 130 Celsius. Now I j have found that by concentrating in a vacu- 1 water, but more readily in hot water, and the I ashes. of a'mixture' of sodium sulfate, sodium sulum the liquid tannin extracts, which are prepared as hereinbefore stated, aproduct is obtained which remaining still ropy in the 5 Celsius solidifies when cooling in such a manner that it may be beaten to pieces with a vacuumat a temperature of about 60 to 65 hammer. The thus-obtained solid tannin extract has a bright dark-colored fracture surface and contains about twenty-two per cent. of water,from sixty-eight to seventy per cent. of tannin, and from five to six per cent.,of The ashes consist for a large portion fite, small amounts of calcic sulfate, and con- The said solid tannin extract dissolves slowly already in cold solutions of 6 to 8 Baumwill not give any precipitate when cooling. Thereby the said solid extracts essentially difier from the hitherto known solid tannin extracts which are not soluble in cold water.

The solutions of the tannin extracts prepared as hereinbefore described are pretty dark colored, and yet impart to the leather a color difiering but slightly from that which is produced by oak tanning. Further, the said solutions have an acid reaction and the addition of organic acids will not produce any precipitate.

Having now described my invention, I claim-- 1. The herein-described process for manufacturing solid tannin extracts soluble in cold 5 5 water, which process consists in treating the crude tannin solution first with alumina sulfate and subsequentlywith'sodium bisulfite, then heating the mixture in a closed receptacle to a temperature between and 6o Celsius and finally concentrating the obtained liquor in a vacuum and cooling the resulting product, substantially as described.

2. Asa new article of manufacture, a solid tannin extract soluble in cold water, which 65 extract contains about sixty-eight to seventy per cent. of tannin, small amounts of sodium sulfate, sodium sulfite and calcic sulfate and about twentytwo per cent. of water and which extract being dark colored and having 7a a bright fracture surface when dissolved in water has an acid reaction and with addition of organic acid and at a strength of 6 to 8 Baum produces no precipitate, substantially as set forth.

In testimony that I claim the foregoing as my invention I have signed my name in presence of two subscribing witnesses.

GEORG KLENK.

Witnesses:

J OHANNES GRoss, OLAUs RANYUNSUN. 

